Imported MP4 Files Have No Audio (Win10)

I've never had this problem before, but now when I try to import MP4 files into Premiere, the audio track comes up empty, doesn't show up at all. It imports it as video only. This happened on an h.264 export that I made on a previous version of Premiere using Mac, and on a video file I created with my webcam using the Windows Camera app. Any ideas what might be going on here? Could the new update have knocked something out of alignment? I'm running fully updated Windows 10 and fully updated Adobe Premiere. Thanks!